Mutsutoshi Kohsaka

Effects of nucleic acid components and their relatives on the excitability of dopamine sensitive giant neurones, identified in subesophageal ganglia of the African giant snail (Achatina fulica Férussac)

Abstract 1. Two dopamine (DA) sensitive giant neurones were identified in the subesophageal ganglia of Achatina fulica Ferussac: the PON (periodically oscillating neurone) excited by DA; and the TAN (tonically autoactive neurone) inhibited by DA. 2. The solutions of nucleic acid components and their relatives (ATP, ADP, AMP, 2′,3′ C-AMP, 3′,5′ C-AMP, 3′,5′ C-AMP dibutyrate, adenosine, caffeine, theophylline, GMP, 3′,5′ C-GMP, CMP, UMP, IMP etc.) were applied on the examined ganglia. 3. Only adenosine, its derivatives and methylxanthines in a high concentration (10 −3 g/ml) showed a slight excitatory effect on the PON, and no substance showed any effect on the TAN. 4. None of the nucleic acid components or their relatives applied ever mimicked the action of DA on the two identified molluscan giant neurones examined.

Amounts of inorganic ions and free amino acids in hemolymph and ganglion of the african giant snail, Achatina fulica Ferussac

Abstract 1. 1. The amount of the principal inorganic ions in the hemolymph of Achatina fulica Ferussac was 5831 ± 57 μ/ml when feeding and 6486 ± 81 μg/ml in starvation. 2. 2. The amount of measured free amino acids in the hemolymph was 0·485 ±0·141 μmoles/ml when feeding and 0·457 ± 0·123 μmoles/ml in starvation. 3. 3. The amount of measured free amino acids in whole subesophageal ganglia (with connective tissue) was 38·3 ± 6·3 μmoles/g when feeding and 30·6 ± 6·7 μmoles/g in starvation. 4. 4. Threonine-serine, alanine and glycine were dominant in the hemolymph and threonine-serine, alanine, lysine and glutamic acid were dominant in the subesophageal ganglia.

Effect of insulin on hyperphenylalaninemia rats

Abstract The influence of insulin on hydroxylation and decarboxylation of tyrosine was examined in control and hyper-Phe rats. Insulin elevated brain tyrosine hydroxylase activity in both control and hyper-Phe rats. Insulin administration also increased the decarboxylation of tyrosine in the brain and liver of control rats. However, decarboxylation did not increase in hyper-Phe rats after insulin injection. Insulin produced a decrement of plasma phenylalanine level and an increment of plasma tyrosine in hyper-Phe rats. These data support our previous study on the therapeutic efficacy of insulin in phenylketonuric patients.

Effect of temperature on human platelet monoamine oxidase

Effect of temperature on human platelet MAO activity was studied by using three different substrates at a temperature range of 12–44°C. The Arrhenius plot of ln Vmax versus 1T yielded a straight line when tryptamine was used as substrate. On the other hand, a nonlinear relationship was observed with both benzylamine and PEA as substrates. This suggests that there are multiple catalytic sites or multiple forms in human platelet MAO.

Diurnal Changes and Aging Effects on Central Monoamine Metabolisms

Studies were conducted on the relation of the daily rhythmicities and aging effect of central monoamine metabolisms using both young (16 weeks) and aged (80 weeks) rats. Every 4 hours during the programmed 12 hour dark and light cycle, animals were sacrificed and dopamine, norepinephrine and serotonin were measured from each of the following six regions; the cerebral cortex, corpus striatum, amygdala, hippocampus, diencephalon and brain stem. Monoamine content showed characteristic circadian or ultradian (biphasic) patterns in many regions and tended to disappear in aged rats especially in norepinephrine in the maximum to minimum ratio. The distinctive changes of monoamine content observed toward the end of the dark or light period (norepinephrine in the cortex and amygdala and some others) may have some consistency with the pre-perceptional increase of motor activity just before the end of both phases. The significant changes observed all through the dark and light cycles in the monoamine content of the aged rats were dopamine in the striatum (64–81% of the amount in the young rats), diencephalon (34–48%) and brain stem (63%), norepinephrine in the brain stem (62–77%). Tyrosine hydroxylase activity was highest in the region of the striatum, where the dopamine content was the highest. Dopamine-β-hydroxylase activities were relatively high in such regions as the hippocampus and the brain stem, where tyrosine hydroxylase activities were low.

Influences of Central Acting Drugs on Δ4-3-Ketosteroid 5α-Oxidoreductase Activity in Rat Diencephalon

Rat diencephalon homogenate was incubated with labeled testosterone in the presence of NADPH. The metabolic product was identified by GLC. TLC and estintation of constant specific activity. Testosterone is converted into dihydrotestosterone. The enzyme involved in this reaction is Δ4‐‐3‐ketosteroid 5α‐oxidoreductase. The optimal pH of Δ4‐‐3‐ketosteroid 5α‐oxidoreductase was 6.8 and the apparent Km value was 2.2 ± 10‐‐6 M. This enzyme showed the highest activity in the microsomal fraction, and it was inhibited up to 85.3 % by progesterone at a concentration of 1 ± 10‐‐5 M.

Effects of Antipsychotic Drugs on Regional Cyclic AMP Levels in the Rat Brain

ABSTRACT In the present study the effects of antipsychotic drugs on regional cyclic AMP content of the rat brain in vivo were examined. A single dose of chlorpromazine (CPZ) inhibited L-dopa-induced increase in cyclic AMP levels of all brain regions examined. Sulpiride had virtually no effect on cyclic AMP levels. In long-term treatment with CPZ for 13 days, L-dopa-induced increase in cyclic AMP levels of CPZ-treated rats was not significantly different from controls 24 hours after the last injection. In contrast, 7 days after cessation of CPZ, cyclic AMP levels in the striatum of CPZ-treated rats significantly elevated in response to L-dopa administration compared with vehicle-treated rats. At this time, L-dopa produced a marked increase in stereotyped behaviors of CPZ-treated rats, while locomotor activity was not different between control and CPZ groups. A similar result was obtained with apomorphine in both biochemical and behavioral measurements. These data suggest that dopaminergic receptor hypersensitivity occurs in the nigrostriatal system, but not in the mesolimbic or mesocortical system after chronic CPZ administration. This might be related to regional differences in the development of tolerance to long-term antipsychotic treatment.